Vaneless supersonic nozzle

ABSTRACT

A converging-diverging nozzle unit for supersonic expansion in turbines is presented wherein a plurality of converging nozzle segments open into a common diverging chamber at or near the throat of the converging nozzles. Convergence and divergence may occur in different directions in the nozzle unit; with reference to a rotating turbine wheel, convergence occurs in a direction substantially tangential with respect thereto, and divergence occurs substantially radial with respect thereto.

United States Patent [191 Sohre VANELESS SUPERSONIC NOZZLE [76]Inventor: John S. Sohre, 93 Grier Rd.,

Vernon, Conn. 06066 [22] Filed: May 21, 1973 [21] Appl. No.: 362,403

[52] US. Cl 239/289, 239/553.5, 415/119,

' 415/181 [51] Int. Cl., B05b 1/34, FOld 1/02 [58] Field ofSearch239/76, 553, 533, 536,

[56] 7 References Cited UNITED, STATES PATENTS 2,258,793 10/1941New...i..... .Q 415/181 UX 2,378,372 6/1945 Whittle 415/181 UX 2,702,1572/1955 Stalker 415/181 X 2,839,239 6/1958 Stalker 415/181 [451 Apr. 16,1974 2,953,295 9/1960 Stalker 415/181 3,744,724 7/1973 Caille 239/5535FOREIGN PATENTS OR APPLICATIONS 342,289 1/1931 Great Britain 415/119615,219 1/1949 Great Britain 415/119 Primary Examiner-Robert S. Ward,Jr.

[57] ABSTRACT A converging-diverging nozzle unit for supersonicexpansion in turbines is presented wherein a plurality of convergingnozzle segments open into a common diverging chamber at or near thethroat of the converging nozzles. Convergence and divergence may occurin different directions in the nozzle unit; with reference to a rotatingturbine wheel, convergence occurs in a direction substantiallytangential with respect thereto, and divergence occurs substantiallyradial with respect thereto.

19 Claims, 15 Drawing Figures 4 PATENTEDAPR 1 6 m4 SHEET 5 BF 5 FIG. 13

1 VANELESS SUPERSONIC NOZZLE BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to the field of turbomachinery. Moreparticularly, this invention relates to the field ofconvergent-divergent nozzle structure for creation and expansion ofsupersonic flow of a compressible fluid for turbine motive fluid.

2. Description of the Prior Art converging-diverging nozzles are neededto create and expand a supersonic stream (at pressure ratios exceedingapproximately 1.85) to transform a high energy stream into a highvelocity jet with good efficiency and minimal shock, flow separation, orjet deflection.

Supersonic shock fronts and jet deflection at pressure ratios abovedesign level, and expansion-compression shock and flow separation atpressure ratios below design level are particular problems inaccomplishing the desired supersonic expansion in turbine machinery, andthese problems have several undesirable consequences, includingdissipation of available energy, unstable flow conditions, inefficientoperation, and imposition of vibratory stress on the associated rotatingturbine blade structure leading to damage thereof. The problem ofvibratory stress of the blade structure is a particularly seriousproblem.

Flow separation results in strong, wide wakes at the nozzle exit,resulting in overall poor efficiency, pressure fluctuations andvibratory loading on the rotating turbine blade structure. Exit edgefailures of the nozzles havealso been encountered.

Jet deflection is a problem particularly associated with pressure ratiosabove design level, and thus there is a direct relationship between jetdeflection and Mach number. Pressure ratio refers, of course, to theratio of the pressure at the inlet of the nozzle to the pressure in thearea into which the nozzle discharges, commonly referred to as thetbackpressure. The exit angle of the fluid from the nozzles is also relatedto and affected by the pressure ratio. The exit angle is the actue angleof the axis of the flow stream with the exit plane of the nozzles. Aturbine is typically designed to operate at a particular pressure ratioand exit angle; and increases in the pressure ratio willcause adeflection of the nozzle jet in a direction to increase the exit angle.This jet deflection can result in shock waves, expansion waves, andpressure gradients with resultant stresses on the buckets, i.e., therotating turbine blades. As a result, blade failures can occur, axialthrust on the rotating structure can increase and fluctuateunpredictably, and an overall highlyinefficient operation results.

Jet deflection also results in an adverse effect on entry of the jetstream into the bucket passages. The cross-sectional area of the jetstream entering the buckets is a direct function of the nozzle exitangle. Jet deflection from increased pressure ratio operation results inan increase in the cross-sectional area of the jet stream entering abucket passage, and the buckets will not function properly if thecross-sectional area of the entering st ream exceeds a design multipleof the throat area of the bucket passage.

Conventional nozzles for convergentsdivergent supersonic expansionare oftwo general types. One type has convergent-divergent profiles machinedinto opposed side surfaces of adjacent nozzles so as to define, in onedimension, convergent-divergent passages between these profiled sidesurfaces. The top and bottom surfaces of such passages are parallel toeach other to define a constant height for the convergent-divergentpassage or the height may vary linear between nozzle inlet and exit. Theother type of conventional nozzle is in the form of round nozzlepassages, as used in drilled and reamed nozzle blocks. These nozzleblocks may be circular in cross-section and thus two-dimensionallyconvergent-divergent. In any case, the divergence and the throat of thepassage are not defined by the inner and outer circumferential walls ofthe passage.

Both of the above discussed general types of convergent-divergentdivergent nozzles do, however, encounter the several problems of jetseparation, jet deflection and vibratory excitation damage to turbineblades. These standard nozzle structures usually .have a very smallspacing from the associated rotating blades; usually on the order ofabout one-sixteenth of an inch. Any shock waves which occur in theexpanding fluid stream must either be dissipated in that narrow space orelse the rotating airfoils are buffeted. Since most of such shockscannot be dissipated in that small space, a great deal of suchundesirable buffeting does occur.

Conventional convergent-divergent airfoil-type nozzles also experienceflow interruptions at the discharge plane because of the physical factthat there must be some spacing (trailing edges) between adjacent flowpaths. This flow interruption also reduces efficiency.

Conventional convergent-divergent nozzle configurations also present acapacity-size problem. In the one dimensional profiled nozzles increasedcapacity is achieved by increasing the width, i.e., by widening thespacing, between contoured surfaces, thus increasing the dimensiontangential with respect to the turbine wheel. In the round nozzles,increased capacity is achieved by enlarging the contoured circularpassages, thus also increasing the tangential dimension. Accordingly,increased capacity invariably results in increased circumferential sizeof the turbomachinery, a result which is often very undesirable, orwhich may result in excessive tip-speeds.

SUMMARY OF TI-IE INVENTION The present invention overcomes or reducesthe above discussed and other problems of the prior art with itssignificantly improved and novel nozzle unit. The nozzle unitconfiguration of the present invention provides a common expansionchamber in conjunction with a plurality of converging nozzle segments.The in dividual diverging passages of conventional converging-divergingnozzles are eliminated and, in their place, a common expansion chamberis provided. The individual converging nozzle segments are connected ator near their throats to the common expansion chamber so that the steamor other turbine propulsive fluid undergoes expansion to the velocity ofsound (Mach 1 in the converging portions of the individual nozzlesegments and is then delivered to the common chamber for supersonicexpansion to the final nozzle exit pressure. The common expansionchamber is a diverging chamber,'but its direction of divergence may beangled, preferably at with respect to the direction of convergence ofthe individual converging nozzle passages. Generally speaking, and withreference to the direction of rotation of the rotating turbine buckets,subsonic expansion is in a direction substantially tangential to theturbine wheel and supersonic expansion utilizes space in a substantiallyradial direction. Thus, convergence and divergence in the nozzle occurin different directions with respect to the direction of flow throughthe nozzle.

If desired, a deflection control wall or, a series of such walls, can beincorporated in the common expansion chamber, inclined in a directionparallel to or substantially parallel to the axis of the desired jetflow at design conditions, and hence inclined oppositely to thedirection of jet deflection normally experienced at increased pressureratios. This deflection control surface will function to prevent thenormal jet deflection usually encountered at pressure ratios above thedesign point and will force the gas to expand and flow in the generaldirection for design conditions. Thus, the usually experienced jetdeflection with its attendant inefficiencies and other problems can beeliminated. Also, and quite sigificantly, the bucket entry angle andcrosssectional area of the entry stream will actually decrease, thusenabling the buckets to function properly over a wider range ofconditions and without an increase of stage reaction (pressure dropacross the buckets).

If desired, the individual nozzle segments can be extended into thecommon expansion chamber to provide a better defined throat and thus amore efficient configuration. However, the major supersonic expansion isstill accomplished by the increase in the radial dimension of the commonexpansion chamber in accordance with the general concept of theinvention.

The nozzle configuration of the present invention with its commonexpansion chamber provides several important advantages over the priorart. The amount of circumferential space and size required to handle agiven amount of steam is reduced, and, similarly, the size increaseneeded to accommodate an increased volume is reduced, because theexpansion is accomplished in the direction of the height of the nozzles,i.e., radial inward and/or outward with respect to the turbine wheel,.rather than in the width separating the nozzles orin the circularconfiguration of the round nozzles.

Accordingly, turbines incorporating the present invention can pass moresteam at higher pressure ratios for a given are of circumference than inthe prior art, and as a result high volumes can be handled at greaterpressure ratios than presently obtainable. Also, machines can be builtwith fewer stages and thus can be smaller and lighter. Overall operatingefficiency is greatly improved because flow interruptions are greatlyreduced or eliminated, and force fluctuations on the buckets are reducedby virtue of the expansion which takes place inthe common passagethereby dissipating wakes and shock effects. It is important to notethat the common expansion passages provide a separation between theindivdual nozzle elements and the buckets much greater than the usualseparation of approximately 1/16 inch to 41 inch found in typical priorart turbines. Byjudicious selection of the location of the trailing edgeof the nozzles, a large common expansion passage can be generated whichis completely free of supersonic shock. Accordingly, efficiency isincreased, and problems of blade stress, bucket vibratory stressexcitation and axial rotor thrust loading are reduced significantly.

Important economic improvements also result from the present invention.Specifically, manufacturing costs can be substantially reduced sinceconventional subsonic profiles can be used for the converging portionsof the nozzles. Also, a high degree of standardization and massproduction can be accomplished since nozzle blocks of the convergingnozzles can be manufactured and stocked irrespective of thepressure-ratio for which they are to be used, and the diverging commonexpansion chamber can be machined or otherwise formed at some latertime, such as at assembly of the final machine, to accommodate thedesired expansion ratio of each individual machine. This eliminatesindividual engineering, drafting and manufacturing of the nozzle blocks.

The common expansion chamber and the radial expansion configuration ofthe present invention can also be incorporated in the rotating bucketstructure of certain turbines. This may be done where supersonicexpansion is desirable to achieve high horsepower output from a minimumnumber of turbine wheels.

Accordingly, one object of the present invention is to provide a noveland improved convergent-divergent nozzle structure for a turbine.

Another object of the present invention is to provide a novel andimproved convergent-divergent nozzle unit for a turbine wherein aplurality of nozzles have a common diverging expansion chamber.

Another object of the present invention is to provide a novel andimproved convergent-divergent nozzle unit for a turbine whereinconvergence and divergence take place in different directions withrespect to the direction of flow through the nozzle.

Still another object of the present invention is to provide a novel andimproved convergent-divergent nozzle structure for turbines whereinproblems of jet deflection, jet separation, vibratory loading and lossof efficiency, commonly encountered in many prior art turbines, aresignificantly reduced.

Still another object of the present invention is to provide a novel andimproved convergent-divergent bucket structure for rotating turbinewheels.

Other objects and advantages will be apparent to and understood by thoseskilled in the art from the following detailed drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings, whereinlike elements are numbered alike in the several figures:

FIG. 1 is a generalized showing, partly in section, of a turbomachineand motive fluid entry passageway;

FIG. 2 is a view taken along line 2-2 of FIG. 1 showing an elevationview of the supersonic convergentdivergent nozzle unit of the presentinvention as applied to stationary nozzles;

FIG. 3 is a view taken along line 3-3 of FIG. 1 showing an arc ofnozzles with their common expansion chamber in accordance with thepresent invention;

FIG. 4 is a view taken along line 44 of FIG. 3;

FIG. 5 is a view similar to FIG. 4 showing a modified wallconfiguration;

FIG. 5A is a cross-sectional view similar to part of FIG. 2 showing thewall contours in the modified configuration of FIG. 5;

FIG. 6 is a view similar to FIG. 3 showing a modified version of theinvention incorporating backup wall;

FIG. 6A is a view showing part of FIG. 6 in detail;

FIG. 7 is a partial view similar to FIG. 3 showing another modificationof the present invention wherein vane elements extend into the commonexpansion chamber;

FIG. 8 is a view along line 8--8 of FIG. 7;

FIG. 9 is a view showing the common expansion chamber of thepresentinvention incorporated in the rotating buckets of a reaction turbinewheel;

FIG. 10 is a view along line l0--10 of FIG. 9;

FIG. 11 is a view similar to FIG. 10 showing a plurality of backupwallsj FIG. 12 is a view along line 12-12 of FIG. 11 showing an enlargedand modified partial view similar to FIG. 9;

FIG. 13 is a view showing the present invention applied to thestationary nozzles and rotating buckets of a turbomachine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2,the general environment of the present invention is shown in the natureof a turbomachin ery unit 10. Turbomachinery unit 10 has an inletchamber 12 to deliver steam or other motive fluid to the unit and aturbine casing 14 for housing a rotating turbine wheel 16 which ismounted for rotation about an axis 18. Many other elements and detailsnormally found in turbomachinery units are unnecessary to a properunderstanding of the present invention, and thus these other detailshave been omitted from the simplified environment shown in FIGS. 1 and2.

Inlet chamber 12 is in flow communication with an array of nozzlesegments 20 which are arranged in an arcuate array on an arccorresponding to the radius of the blades or buckets 24 of turbine 16with respect to axis 18. The individual nozzle segments 20 form part ofa convergent-divergent nozzle unit 22 which serves to direct the steamor the motive fluid from inlet chamber 12 to the blades or buckets 24 ofturbine wheel 16. Convergent-divergent nozzle unit 22 is comprised ofthe individual nozzle segments 20 which cooperate with each other toform a plurality of convergent flow paths 21, and a common divergingexpansion chamber 26 which is in flow communication with the convergentpaths 21 between the nozzles 20. The steam or other motive fluid flowsthrough inlet chamber 12 into the convergent flow paths between adjacentnozzles 20, and that flow may, if desired, be regulated by appropriatecontrol valving. The motive fluid is subsonically expanded in traversingthe converging passageways between adjacent nozzles, and it is thensupersonically expanded in chamber 26 and then delivered to the buckets24 to drive turbine wheel 16.

As can be seen from a combined consideration of FIGS. 1, 2, 3 and 4, thewidth between adjacent nozzles 20 diminishes, and hence the passageways21 converge, in a direction generally tangential with respect to turbinewheel 16. The radial height of vanes 20, Le, the dimension in adirection along a radius of turbine wheel 16 is defined by separationbetween the left portions of walls 28 and 30, and that radial height isshown constant in FIG. 2 (although it could bevaried if desired).Conversely, of that part of the walls 28 and 30 which define chamber 26,at least one of those walls, i.e., the right portion of wall 28 in FIG.2, is inclined with re spect to a radius of the turbine wheel so thatchamber 26 canbe said to expand radially with respect to the turbinewheel. Of course, wall 30 could, if desired, also be inclined so thatchamber 26 would expand both toward axis 18 as well as in the directionaway from axis 18. Wall 28 terminates in a segment 32 which isperpendicular with respect to the radius of wheel 16, and section 32cooperates with a similar length of wall 28 to form a nozzle exitpassage with an exit edge 33 immediately adjacent to the rotating wheel16 and blades 24. Of course, it should be kept in mind that the nozzles20 are arranged in an arcuate array, and that walls 28 and 30 aresimilarly arcuate to conform with the annular array of turbine blades24.

Referring now to FIG. 3, a view of the nozzle unit is presented takenalong 33 of FIG. 1. The array of individual nozzles 20 formingconverging flow paths 21 therebetween can be seen, and these convergingflow paths 21 are seen communicating with the common expansion chamber26. A throat 34 is defined in each passage 21 at the plane of smallestcross-section area of the passage, and the throat 34 of each convergentpassage 21 communicates directly with the common expansion chamber 26.The width of flow passages 21 is defined by the separation betweenadjacent nozzles, and the height of flow passages 21 is defined by theseparation between the left portion of walls 28 and 30.

Referring collectively to FIGS. 1-4, the necessary convergent-divergentstructure is present in nozzle unit 22 for supersonic expansion of acompressible medium. The steam flows through inlet chamber 12 and theninto convergent passageways 21 defined by the confronting walls ofadjacent nozzle segments 20. The throats of passageways 21 are connectedto expansion chamber 26, and the fluid in each of the passageways isdelivered into the common diverging expansion chamber which, asindicated above, expands in a direction angled, preferably perpendicularwith respect to the direction of convergence effected by nozzle segments20. Stated in another way, convergence and divergence in the nozzleoccur in different directions, preferably mutually perpendiculardirections, with respect to the direction of flow through the nozzle, orit can be said that planes extending in the direction of convergence anddivergence intersect at approximately As indicated above, conventionalconvergentdivergent nozzle configurations typically terminate close tothe associated blades, the separation usually being somewhere on theorder of about 1/16 to A; of an inch. By way of significant distinction,nozzle segments 20 terminate a substantial distance from turbine blades24. While that distance will, of course, vary for different designs, itwill typically be on the order of several inches, such as from V2 to 10or more inches, so that chamber 26 is of substantial length normal toturbine wheel 16. The radially expanding nature of chamber 26 providesthe necessary volume to accommodate the superonic expansion of the fluidbeing discharged from each of the passageways 21 to transform the highenergy levels of the fluid into a high-velocity jet for deliva ery tothe turbine buckets 24. Since the trailing edges of the nozzles may belocated in a subsonic region, this will eliminate all supersonic shockwaves in the entire supersonic expansion passage 26. The length ofchamber 26 provides a long vaneless passage in which the superonicexpansion is taking place, and this vaneless passage accomplishes flowadjustment and dissipation of wakes, shock waves, expansion waves andpressure gradients, thereby significantly improving the overallefficiency of the machinery and significantly reducing the problems ofvibratory loading, blade and nozzle failures and rotor thrust loadingwhich have accompanied jet deflection and flow separation in the priorart. The problems previously encountered with flow interruption are alsoreduced or eliminated since the long vaneless passage 26 produces asubstantially uniform continuous combined flow stream for delivery tothe buckets 24. The walls 28 and 30 appear to be curved as seen in FIG.4 because of the location of line 44 in FIG. 3.

Referring now to FIGS. 5 and 5A, a modified configuration is shownwherein walls 28 and 30 are slightly curved as seen in FIG. 5A, thusresulting in an apparently straight configuration when viewed as in FIG.5. This modified shape has Prandtl corners at the junctions of walls 28and 30 with throat 34. These are some times considered desirable becausethey illustrates the exact point of onset of supersonic expansion. Otherconfigurations can be obtained in a similar manner. This exampleillustrated the capability of the invention to accommodate a wide rangeof thermodynamic requirements with only minor changes of hardwareconfiguration. A wide variety of conditions can thus be accommodatedwithout a change in nozzle segments 20.

Referring now to FIG. 6, a view similar to FIG. 3 is shown incorporatinga modification in the form of a backup deflection control wall 36 in thecommon expansion chamber 26. Wall 36 functions to control jet deflectionat pressure ratios above design level. The angle or shown in FIG. 6represents the angle between the flow axis of a discharge stream from apassage 21 and the discharge plane from the nozzles. With prior artnozzle configurations, an increase in the pressure ratio P IP wouldresult in an increase in the angle a with attendant shock wave and flowseparation development leading to inefficient operation at off designconditions. With the presence of backup wall 36, a reduction in P (thusresulting in an increase in the ratio of P /P results in wall 36functioning to produce a decrease in angle a at the end of the steam-jetremoved from wall 36, so that the discharge from nozzles fills thevolume which is available in the diverging chamber 26. This reduction inangle a is directly opposite to the effect normally encountered and maybe termed a negative deflection; it results from the fact that thepresence of backup wall 36 prevents the normal jet deflection and forcesthe gas to expand in the opposite direction to decrease angle a. Sincethe angle a thus adjusts as a function of the ratio P /P in a directionopposite to that previously encountered, the commonly experienced shockand flow separation problems are avoided or reduced for off designconditions, and thus the nozzle unit of the present invention results ina significant improvement in nozzle efficiency.

Referring both to FIGS. 6 and 6A, another very significant advantage ofthe modified configuration incorporating backup wall 36 is shown. Amajor problem heretofor encountered in supersonic bucket entry relatesto a relationship between the area f, of the entering stream (determinedin the plane normal to the direction of the flow stream from the nozzledischarge to the bucket) and the cross-sectional area f of the flowpassage between adjacent buckets. If the ratio f exceeds a certainlevel, the bucket will not function properly. As can be seen in FIG. 6A,an increase in a a condition normally encounted in the prior art,results in an increase in f,, and the buckets will not function properly(or choke) if that increase becomes excessive. With the presence ofbackup wall 36, an increase in P /P (with its attendant increase in Machnumber) will result in a reduction in a and thus a reduction in fAccordingly, the buckets can continue to function properly without thegeneration of a reaction pressure drop and/or choking over a much widerrange of Mach number and pressure ratio conditions than heretoforepossible.

While only one backup wall is shown in FIG. 6, it will be understoodthat a plurality of such backup walls can be incorporated, distributedperiodically or aperiodically along the nozzle array. Up to as many asone backup wall for each two nozzles can be used, in which event therewould be a backup wall extending from every other nozzle toward thebuckets.

Referring now to FIGS. 7 and 8, still another modification of thepresent invention is shown. In this modification the trailing edges20(a) of the nozzles 20 are continued beyond throat 34 into divergentchamber 26, and they may extend partway into the chamber. The passage 40formed between the trailing edges may be parallel sided, converging ordiverging, straight or curved. In any of these events, and as can bestbe seen in FIG. 8, the major part of total divergence, and hence gasexpansion, between throat 34 and exit edge 38 is still accomplished inthe radial direction by the presence of sloping wall 28, and the passagethroat is also defined by walls 28 and/or 30. Of course, as previouslyindicated, wall 30 can also be sloping in the direction opposite to theslope of wall 28. The extension of trailing edges 20(a) into the commonradially extending expansion chamber 26 provides a somewhat betterdefined throat for the passageways 21 thus contributing to increasedefficiency. As pointed out above, it will, however, still be noted thatthe major expansion in chamber 26 still occurs in a directionperpendicular to the passage formed by the nozzle-profiles 20 from theentry of the nozzles to throat 34.

As is discussed in more detail with regard to FIG. 12, the location ofthe throat, i.e., the smallest crosssectional flow area, can be definedby contouring one or both of the wall segments 28(a) and 30(a) upstreamof the throat. In this manner the throat, indicated at 34(a) in FIG. 8,can be defined in the radial plane with respect to the turbine wheel byvarying the passage walls upstream of the throat rather than by varyingthe separation between the vanes as is now done in the art. This wallcontouring to define the throat is shown in the dotted lines in FIG. 8,but it will be understood it can be incorporated in any of theembodiments of the invention.

Still referring to FIG. 8, total supersonic expansion can be adjustedand determined by varying the height of the expansion chamber, i.e., byvarying the distance between walls 28 and 30. As seen in FIG. 8, thecontouring of wall 28 in the solid line will result in one expansionratio, while contouring of wall 28 in the dotted line will result in adifferent expansion ratio. Thus, the present invention makes it possibleto vary expansion ratios by varying the height of the expansion chamberrather than by varying the separation between nozzles as is presentlydone in the art. It thus becomes possible with the present invention tostock standard nozzle blocks and use those standard nozzle blocks ininstallations where different expansion ratios are required and arerealized by contouring the radial height of the expansion chamber. Thisability to use standard nozzle blocks in installations of differentexpansion ratios is a very significant economic advantage since itgreatly reduces the cost experienced in the prior art of customizingnozzle blocks.

In all of the embodiments of the invention discussed above, higherefficiencies can be realized than in the prior art, and many of theprior art problems of jet deflection, flow separation, flowinterruption, vibratory stressing and blade damage can be significantlyreduced, especially for off design conditions. In addition, much lesscircuinferential space is required so that more power can be produced inless space because the direction of nozzle height, i.e., the radialdirection with respect to the turbine wheel, is used to accomplish thesupersonic expansion. Accordingly, the design of the prevent inventioncan handle more steam at higher pressure ratios for a given are ofcircumference of the turbine wheelthan heretofor possible. Significanteconomies can be realized in that conventional subsonic profiles can beused for the nozzle segments 20, and finished blocks of such nozzles canbe premanufactured and stocked with the diverging chamber 26 beingmachined or otherwise formed at assembly to accommodate the expansionratio of each individual machine. Thus, individual engineering, draftingand manufacturing of each nozzleblock can be eliminated.

Referring now to FIGS. 9 and 10, the present invention is'shownincorporated in the rotating wheel of a pure reaction turbine which hasno stationary nozzles. The turbine wheel 50 is mounted forrotation on ashaft 52 and it carries anannular array of spaced buckets 54. Thebuckets 54 arerotated in wheel 50 at their inner ends, and the outerends of the buckets are joined to a common annular shroud 56 which formspart of the rotating assembly. Shaft 52 and shroud 56 are sealed byappropriate seals 58 and 60, respectively, so high pressure steam orother motive fluid can be delivered to and expanded through the bucketsin the flow direction with respect to the previous embodiments, it willbe understood that the buckets may terminate at the throat or may extendany desired distance into the common expansion chamber.

As has been discussed with respect to the previous embodiments relatingto stationary nozzles, the embodiment of FIGS. :9 and has a commonexpansion chamber; i.e., chamber 70, into which all of the bucketsdischarge. Thus, subsonic expansion takes place in the individual flowpassages 62, in a direction substantially tangential with respect to aradius of a turbine wheel. However, the walls 64 and 66 which definecommon expansion chamber 70 are inclined with respect to a radius of aturbine wheel so as to define a radially expanding chamber wherein thesupersonic expansion oocurs in a direction which can be consideredradial with respect to the turbine wheel. Of course, it will beunderstood that the common expansion chamber is an annular chamberaround the entire turbine wheel, only part of which has been shown inFIGS. 9 and 10.

This configuration wherein a vaneless supersonic expansion chamber isincorporated in a rotating turbine wheel is desirable to obtain a highhorsepower output from a minimum number of wheels. The turbine wheel maybe a pure reaction turbine having no stationary nozzles, as shown inFIGS. 9 and 10, or it may also be used in conjunction with a nozzleassembly of either the vaneless supersonic nozzle type of the presentinvention or a conventional prior art nozzle configuration. While bothof walls 64 and 66 are shown diverging to form chamber 70, it will beunderstood, as discussed previously, that the radial divergence ofchamber 70 can also be realized with only one of these walls inclined.

Referring now to FIG. 1 l, a modification of FIG. 10 is shown whereinbackup walls 71 are incorporated. These backup walls are comparable tothe backup walls described above with regard to FIG. 6. The backupwalls, which define vaneless supersonic expansion chambers therebetween,may be distributed periodically or aperiodically about the circumferenceof chamber 70, with the number of backup walls varying from as few astwo for the entire circumference to as many as one for each two buckets.Two of the backup walls 70 are shown in FIG. l l representative of anarrangement wherein a backup wall is positioned at every third nozzle.In that arrangement for backup walls, each two adjacent backup wallswould define a common radially diverging expansion chamber for the threeflow paths 62 contained therebetween.

Referring now to FIG. 12, an arrangement is shown wherein the blades 54cooperate with a stationary shroud 72, the wall 74 of which cooperateswith wall 64 to define the contour of flow passage through the bucketsand also to define the contour of the common supersonic expansionchamber 70. As'can be seen in FIG. 12, and with reference tov thedirection of flow through the turbine, the left portion of wall 74 isinclined toward or converging with respect to wall 64, and the rightportion of wall 74 is inclined away from or diverging with respect towall 64. This converging-diverging shape of wall 74 can be used todefine the throat 68 of the passageway at any desired point by adjustingthe contour of wall 74 (or wall 64) to form the narrowestcross-sectional flow area of the passage at the desired location of thethroat. Thus, by the modification shown in FIG. 12, which is similar tothe modification discussed with respect to and illustrated in the dottedconfiguration of FIG. 8, the location of the throat of the bucket ornozzle, as the case may be, can be defined in the radial plane, i.e.,radially with respect to the turbine wheel, by contouring either the topor bottom wall which defines the flow passage rather than by the contourof the side walls. Among other advantages, this modification affords theadvantage that alarge number of buckets or nozzles may, if desired, bearranged in an array with a smaller than usual spacing therebetween, andthe additional necessary space for the flow passage volume can beobtained by the radial contouring of the co verging partof the passagewherein the subsonic expansion takes place. The wall contouring aspectsof FIG. 8 an'iiz' with respect to con touring of the individual flowpassages are more fully discussed and claimed in my copendingApplication Serial No. 362,402 filed contemporaneously herewith,lieferring now to FIG. 13, an arrangement is shown, for purposes ofillustration only, wherein the concepts of the present invention areshown in both the rotating and stationary stages of a turbomachineryunit in a highly efficient manner and for a very large pressure ratio,such as on the order of 1000:l. The turbomachinery unit of FIG. 13 hasan inlet generally designated at 76, a first rotating stage 78, astationary stage 80, a second rotating stage 82, and an exit 84. Therotating stages 78 and 82 may be of the type shown in FIG. 12 withturbine wheels 50 mounted on a common rotating shaft 52, each of thewheels carrying buckets 54 and cooperating with contoured shrouds 72which serve to define the supersonic expansion passages 70 and whichmay, if desired, also define the contour of the subsonic expansionpassages. Between the two rotating stages stationary stage 80 hasstationary nozzles and the common supersonic expansion chamber 26.Backup walls may be included as indicated in the dotted lines.

In the arrangement shown in FIG. 13, a fluid entering inlet 76 at 1,000psia can be expanded through rotating stage 78 to 100 psia, and can thenbe expanded through stationary stage 80 to 10 psia and can then beexpanded through rotating stage 82 to l psia. Thus, a 10:1 expansion canbe accommodated in each of three stages to accommodate an overallpressure ratio of 1,000: l and this can be accomplished using only tworotating rows and one stationary row. Of course, it will be understoodthat the arrangement shown in FIG. 13 is for illustrative purposes only,and many other and varied arrangements can be accomplished depending onthe design requirements for particular installations.

While the discussion herein has been directed to an axial machine; i.e.,one in which the motive fluid flows through the turbine wheel in agenerally axial direction, it should also be noted that the invention isequally applicable to a radial'machine, i.e., one in which the motivefluid is delivered generally tangentially to the turbine wheel. In suchan arrangement, for example, convergence could 'occur in a directiongenerally parallel to the turbine wheel and divergencecould occur in adirection 90 removed and generally perpendicular to the wheel.

While a preferred embodiment has been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the present invention. Accordingly, it maybe seen that the present invention has been shown and described by wayof illustration and not limitation.

What is claimedis:

I. A converging-diverging nozzle unit for supersonic expansion of amotive fluid for delivery to a turbine wheel, the nozzle unit including:

a plurality of nozzles in an array with converging flow passages betweenadjacent nozzles in the array;

an entrance and a throat in each of said flow passages, the throat beingdownstream of the entrance in the direction of flow of motive fluidthrough the passage; and

a common diverging expansion chamber connected L to receive flow fromsaid converging passages, said common diverging chamber extending fromthe vicinity of the throats of said converging passages downstreamtoward the turbine wheel.

2. A converging-diverging nozzle unit as in claim 1 wherein:

said common diverging expansion chamber diverges in a directiongenerally radial with respect to the turbine wheel. 3. Aconverging-diverging nozzle unit as in claim 2 wherein:

said converging flow passages converge at least partly in a direction atan angle with respect to the direction of divergence of said commondiverging chamber. 4. A converging-diverging nozzle unit as in claim 3wherein:

said converging flow passages converge in a direction generallytangential with respect to the turbine wheel. 5. A converging-divergingnozzle unit as in claim 3 wherein:

said angle between the direction of divergence of said diverging chamberand the direction of convergence of said converging chamber isapproximately 6. A converging-diverging nozzle unit as in claim 1wherein:

adjacent nozzles extend downstream of the throat defined therebetweenand extendinto said common diverging chamber. 7. A converging-divergingnozzle unit as in claim 1 including:

at least one backup wall in said common expansion chamber. 8. Aconverging-diverging nozzle unit as in claim 7 wherein:

said backup wall is inclined at an angle to reduce the angle between theflow axis of a discharge stream from a flow passage and the exit planeof the passage upon an increase in the pressure ratio across the nozzleunit.

9. A converging-diverging nozzle unit as in claim 8 including:

a plurality of backup walls in said common expansion chamber, any twoadjacent backup walls being spaced apart to include at least two flowpassages therebetween.

10. A converging-diverging nozzle unit as in claim 1 wherein:

said passages in said nozzle converge in a first direction with respectto the turbine wheel; and

said common diverging expansion chamber diverges in a second directionwith respect to said turbine wheel and at an angle with respect to saidfirst direction.

1 l. A converging-diverging nozzle unit as in claim 10 wherein:

said second direction is at an angle of approximately 90 with respect tosaid first direction.

12. A converging-diverging nozzle unit for supersonic expansion of amotive fluid for delivery to a turbine wheel, the nozzle unit including:

a plurality of nozzle means arranged in an arcuate array with convergingflow passages defined between adjacent nozzle means for subsonicexpansion of a motive fluid;

an entrance and a throat in each of said flow passages, the throat beingdownstream of the entrance in the direction of motive fluid flow throughthe passages; and

common expansion chamber means between said array of nozzle means andthe turbine wheel for su- 13 14 personic expansion of motive fluid fromsaid nozzle vergence of said converging chamber intersect at means anddelivery to the turbine wheel, said coman angle of approximately 90. monexpansion chamber means having inner and 16. A converging-divergingnozzle unit as in claim 12 outer arcuate walls spaced apart in adirection subwherein: stantially radial with respect to the turbinewheel, adjacent nozzles extend downstream of the throat deat least oneof said inner and outer arcuate walls fined therebetween and extend intosaid common being inclined away from the other along at least divergingchamber. part of its length whereby said common expansion 17. Aconverging-diverging nozzle unit as in claim 12 chamber diverges betweensaid array of nozzle including: means and said turbine wheel. at leastone backup wall in said common expansion 13. A converging-divergingnozzle unit as in claim 12 chamber. wherein: 18. A converging-divergingnozzle unit as in claim 17 said converging flow passages converge atleast partly wherein:

in a direction at an angle with respect to the direcsaid backup wall isinclined at an angle to reduce the tion of divergence of said commondiverging chamangle between the flow axis of a discharge stream her.from a flow passage and the exit plane of the pas- 14. Aconverging-diverging nozzle unit as in claim 13 sage upon an increase inthe pressure ratio across wherein: the nozzle unit.

said converging flow passages converge in a direction 19. Aconverging-diverging nozzle unit as in claim 18 generally perpendicularwith respect to a radius of 20 including:

the turbine wheel. a plurality of backup walls in said common expansion15. A converging-diverging nozzle unit as in claim 13 chamber, any twoadjacent backup walls being wherein: spaced apart to include at leasttwo-flow passages planes extending in the direction of divergence oftherebetween:

said diverging chamber and the direction of con-

1. A converging-diverging nozzle unit for supersonic expansion of amotive fluid for delivery to a turbine wheel, the nozzle unit including:a plurality of nozzles in an array with converging flow passages betweenadjacent nozzles in the array; an entrance and a throat in each of saidflow passages, the throat being downstream of the entrance in thedirection of flow of motive fluid through the passage; and a commondiverging expansion chamber connected to receive flow from saidconverging passages, said common diverging chamber extending from thevicinity of the throats of said converging passages downstream towardthe turbine wheel.
 2. A converging-diverging nozzle unit as in claim 1wherein: said common diverging expansion chamber diverges in a directiongenerally radial with respect to the turbine wheel.
 3. Aconverging-diverging nozzle unit as in claim 2 wherein: said convergingflow passages converge at least partly in a direction at an angle withrespect to the direction of divergence of said common diverging chamber.4. A converging-diverging nozzle unit as in claim 3 wherein: saidconverging flow passages converge in a direction generally tangentialwith respect to the turbine wheel.
 5. A converging-diverging nozzle unitas in claim 3 wherein: said angle between the direction of divergence ofsaid diverging chamber and the direction of convergence of saidconverging chamber is approximately 90*.
 6. A converging-divergingnozzle unit as in claim 1 wherein: adjacent nozzles extend downstream ofthe throat defined therebetween and extend into said common divergingchamber.
 7. A converging-diverging nozzle unit as in claim 1 including:at least one backup wall in said common expansion chamber.
 8. Aconverging-diverging nozzle unit as in claim 7 wherein: said backup wallis inclined at an angle to reduce the angle between the flow axis of adischarge stream from a flow passage and the exit plane of the passageupon an increase in the pressure ratio across the nozzle unit.
 9. Aconverging-diverging nozzle unit as in claim 8 including: a plurality ofbackup walls in said common expansion chamber, any two adjacent backupwalls being spaced apart to include at least two flow passagestherebetween.
 10. A converging-diverging nozzle unit as in claim 1wherein: said passages in said nozzle converge in a first direction withrespect to the turbine wheel; and said common diverging expansionchamber diverges in a second direction with respect to said turbinewheel and at an angle with respect to said first direction.
 11. Aconverging-diverging nozzle unit as in claim 10 wherein: said seconddirection is at an angle of approximately 90* with respect to said firstdirection.
 12. A converging-diverging nozzle unit for supersonicexpansion of a motive fluid for delivery to a turbine wheel, the nozzleunit including: a plurality of nozzle means arranged in an arcuate arraywith converging flow passages defined between adjacent nozzle means forsubsonic expansion of a motive fluid; an entrance and a throat in eachof said flow passages, the throat being downstream of the entrance inthe direction of motive fluid flow through the passages; and commonexpansion chamber means between said array of nozzle means and theturbine wheel for supersonic expansion of motive fluid from said nozzlemeans and delivery to the turbine wheel, said common expansion chambermeans having inner and outer arcuate walls spaced apart in a directionsubstantially radial with respect to the turbine wheel, at least one ofsaid inner and outer arcuate walls being inclined away from the otheralong at least part of its length whereby said common expansion chamberdiverges between said array of nozzle means and said turbine wheel. 13.A converging-diverging nozzle unit as in claim 12 wherein: saidconverging flow passages converge at least partly in a direction at anangle with respect to the direction of divergence of said commondiverging chamber.
 14. A converging-diverging nozzle unit as in claim 13wherein: said converging flow passages converge in a direction generallyperpendicular with respect to a radius of the turbine wheel.
 15. Aconverging-diverging nozzle unit as in claim 13 wherein: planesextending in the direction of divergence of said diverging chamber andthe direction of convergence of said converging chamber intersect at anangle of approximately 90*.
 16. A converging-diverging nozzle unit as inclaim 12 wherein: adjacent nozzles extend downstream of the throatdefined therebetween and extend into said common diverging chamber. 17.A converging-diverging nozzle unit as in claim 12 including: at leastone backup wall in said common expansion chamber.
 18. Aconverging-diverging nozzle unit as in claim 17 wherein: said backupwall is inclined at an angle to reduce the angle between the flow axisof a discharge stream from a flow passage and the exit plane of thepassage upon an increase in the pressure ratio across the nozzle unit.19. A converging-diverging nozzle unit as in claim 18 including: aplurality of backup walls in said common expansion chaMber, any twoadjacent backup walls being spaced apart to include at least two flowpassages therebetween.